Post on 30-May-2018
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A project seminar
on
performance analysis & implementation of
AMR- WIDEBAND SPEECH CODEC
PERFORMED BY
(1) Kapadia Kunal R. (6229) (2) Desai Chintan B. (6211)
(3) Desai Jaimin B. (6212) (4) Chopra Dhikant R. (6208)
GUIDED BY
(Prof. Ninad S. Bhatt)
(Mr. Vijayendra A. Desai)
ELECTRONICS & COMMUNICATION ENGINEERING DEPARTMENT
OF
C.K.PITHAWALA COLLEGE OF ENGINEERING & TECHNOLOGY,
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Problem statement:To design &implement AMR-WB.
We are going to implement AMR WIDEBAND USINGMATLAB. We have started our work with AMR & VAD. IN our project we will used following ALGORITHM :
I. LPC (LINEAR PREDICTIVE CODING)II. CELP (CODE EXITED LINEAR PREDICTIVE CODING)III. ACELP (ALGEBRIC CODE EXITED LINEAR PREDICTIVE
CODING )
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speech coding is a procedure to represent a digitized speech signal using
as few bits as possible, maintaining at the same time a reasonable level ofspeechquality.
SPEECHCODERS
ccording to bit rate according to coding technique
High bit rate >15kbpsMedium bit rate 5 to 10kbpsLow bit rate 2 to 5kbpsVery low bit rate < 2kbps
Waveform codersParametric codersHybrid coders
Requirements of speech coders
Low bit rateHigh speech qualityRobustness across different speakersRobustness in the presence of channel errorGood performance on non speech signals
Low memory size & low computational complexityLow coding delay
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asic block diagram of speech coding :
FILTER SAMPLERA/D
CONVERTER
SOURCEENCODE
R
CHANNEL
ENCODER
CHANNEL
CHANNELDECODER
SOURCEDECODE
R
D/ACONVETER
FILTER
SPEECH
OUTPUTSPEECH
Limitation of other basic speech coders SORCE CODER & CHANNEL CODER WORK SEPARETELY.
SolutionIN AMR, THIS LIMITATION OVERCOME THE PROBLEM OF SOURCE CODER & CHA
CODER WORKING SIMULTANEOUSLY.
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AMR(ADAPTIVE MULTI RATE ):
AMR is a technique to maintain good voice quality invarious conditions of channel.
It is a technique which increases voice quality andboosted channel error robustness and capacity.
Why AMR is used?
IN CELLULAR COMMUNICATION, quality of voice is mostimportant.It depends on channel condition.Bad channel condition produces many error.TO maintain voice quality in different channel condition AMR
is required.
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BASIC DIAGRAM OF AMR CODECSYSTEM :
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OPERATION OF AMR :
AMR FULL RATE:[BIT RATE22.8kbps]
Total 8 modes of operation From 12.2 kbps to 4.75kbps In worst channel conditio:4.75kbps In best channel condition: 12.2kbps
AMR HALF RATE:[BIT RATE11.4kbps]
Total 6 modes of operation From 7.95 kbps to 4.75kbps In worst channel condition:4.75kb In best channel condition: 7.95kbp
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LINK ADAPTION & IN-BANDSINGALLING: IT CONSISTS OF CHANNEL QUALITY MEASUREMENT & CODEC MODEALGORITHM.
IT ADAPTS BIT PARTITIONING BETWEEN CHANNEL & SPEECH CODING.DEPENDING ON C/I, LINK ADAPTION SELECT THE OPTIMAL CODEC &CHANNEL MODE. C/I
(dB)AMR
MODE(kb/s)
>=8 12.2
>=5
7.95
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VAD (VOICE ACTIVITYDETECTION):IT IS A TECHNIQUE USED IN SPEECH PROCESSING WHEREIN
THE PRESENCE OR ABSENCE OF HUMAN SPEECH IS
DETECTED IN REGION OF AUDIO. Features of VAD:
LINE SPECTRAL FREQUENCIES FULL-BAND ENERGY
LOW-BAND ENERGY(
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FILTERBANK &
COMPUTATION OF SUB
BANDLEVELS
PITCHDETECTION
TONEDETECTION
COMPLEXSIGNAL
ANALYSIS
VADDECESION
S(i)
T_OP[n]
T0,t1
OL-LTPCorrelati
on vector
level[n]
pitch
tone
Complexwarning
Complextimer
VADFLAG
BLOCK DIAGRAM VADALGORITHM:
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A. NOISE REDUCTION, e.g. via spectral subtraction.B. FEATURES OR QUANTITIES ARE CALCULATED FROM A SECTION OF
SIGNAL INPUT.C. DETECT WHETHER SPEECH IS TRANSMITTED OR NOT.
DESIGN OF VAD ALGORITHM:
FILTER BANK: Input signal is divided into frequency band usinga 9 band filter bank.
PITCH DETECTION: IT detects vowel sounds & other periodicsignal.TONE DETECTION: IT detects information tone.COMPLEX SIGNAL ANALYSIS: It detects correlated signals inthe high pass filtered weighted speech domain.
VAD DECESION: After comparing with threshold value it givesVAD output.
OVERVIEW OF VAD BLOCK DIAGRAM:
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WEB SUPPORT:
En.wikipedia.org www.vocal.com www.3gpp.org
REFERENCES:
BOOK SUPPORT
Speech Coding Algorithms Foundation and Evolution ofStandardizatied Coders by Wai C. Chu,A John Wiley &Sons,2003 Wireless Communication Principle and Practice by Theodore S.Rappaport, 2005
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HANK YOU!!!